Process of constructing permanent magnets



F. A; SWANSONI.

' PROCESS OF CONSTRUCIING PERMANENT MAGNETS.

APPLICATION FILED MAY 20. 1920.

1 ,432,920 Patented Oct. 24,1922.

IIJVENTOR flank A. Swat/2301a ML m A TTOR/V E FRANK A. swnnson, or nnwanir, new

ASSIGI IONJ Ti) SPLII'DORF ELEC- TnIoAL German's, or nnwnnn, n'n'v IPROCESS OF CONS IJEUGTING Application filed May 2G,

T 0 all whom it may concern I Be it known that i, FRANK In Swanson, a citizen of the United States, residing at Newark, in the county of Essex, of New Jersey, have invented certain new and useful Improvements in Processes of Constructing Permanent Magnets, of whichtl e following is a description, reference being had to the accompanying drawing and to the figures of reference marked thereon.

My invention relates to the process of manufacturing permanent magnets particularly of the type used on magneto generators used for ignition purposes. In generators of this character the magnets are usually of the horseshoe type and are constructed to fit very snugly over magnetic field poles or some member used for collecting the magnetic flux from the magnets and distributin; it through the generating coil structure. This means that the distance between the limbs of the magnet must be smooth and accurate so that the said limbs will fit very closely the pole pieces or member as above described. In order to get close fitting magnets it has been customary to form the nets so that the distance between the limbs is something less than the actual distance to be embraced by the limbs and then grind the interior surface of the said limbs until the proper distance between the limbs is secured. According to past methods it has been customary to grind a much farther distance up on the limbs of the magnet than that embraced by the pole pieces or other member in order to insure that the magnets would go into position. This method of grinding is apt to produce a taper eifect, that is to say, the inner ground surfaces would not be parallel thereby making the ends of the limbs a looser fit on the pole pieces than some point farther up, when,- as a matter of fact the magnet pole itself is near the end of the limbs where a good contact ought to be secured.

It is the object of my invention to provide a process for making magnets so that V the bearing surfaces shall be true/and parallel and in which the minimum amount of grinding need be done, with consequent less wear on the grinders with considerable savin in time.

My invention is exemplified in the drawings, in which Flgure 1 1s a view of the horseshoe magnet illustrating my improved pronnn'r ritaennrs.

Serial in. 383,023,

and Figure 2 is a side View of Figure l. iiigure 3 shows the lower end of one limb ngs 1 illustrates a horseshoe magnet havingportions cut out at 2 and 3 for a particular type of magnet. After the magnet has been formed to the U shape and while still hot or it may be heated again to the desired temperature, it is placed in a proper tool or fixture and operated on by suitable mechanism so that the ends of the limbs are offset towards each other a suitable distance as at l and 5 from ten to fifteen thousandths of an inch. Preferably both limbs are offset simultaneously by one operation. After one magnets have been hardened they are then placed on a grinder usually of the disc type and part of the offset portions is ground off to a point as illustrated by the dotted lines 6 and 7, which indicate the required distance between the limbs of the magnet but which are still nearer together than the surfaces 8 and 9 immediately above the ground off portions- 6 and 7, in some cases the distances may be the same.

it is to be understood that instead of olfsetting the entire end of the limbs of the magnet as shown in the drawing a boss of suitable area may be indented inwardly on each limb at a point substantially near the magnetic poles.

This particular construction is illustrated in Figs. 3 and f wherein the portion or boss 10 is indented inward.

.lin some cases the indentations or offset portions may be made accurately enough so that little or no grinding is necessary but in these cases it is desirable to take the scale, formed during the hardening operation, off by some suitable process, such as sand blast ing.

It will be seen by this'process that the disc grinders can be operated more advantageously, because the rim of the disc will not be cutting as in the old method, but all the work will be taken on the side of the grinder here shoe magnets, which consists,

magnets, Which consists in offsetting the end portion of the magnet and then subsequently each other, then subsequently grinding off on the inner sides a part of the olfset portions to true surfaces a fixed distance from each other.

4-. The process of constructing permanent horseshoe magnets, Which consists, in heating the magnets to a suitable temperature, then acting on the ends of both limbs of the magnet simultaneously with a suitable tool to force the ends of the limbs a certain dis tance toward each other, then subsequently grinding off on the inner sides a part of the offset portions to true surfaces a fixed distance from each other.

In testimony whereof, I affix my signature FRANK A. SWANSON. 

